Perovskites as Alternatives to Noble Metals in Automotive Exhaust Abatement: Activation of Oxygen on LaCrO 3 and LaMnO 3

In this contribution, perovskitic materials have been tested as substitutes of noble metals in automotive exhaust abatement devices. LaMnO 3 and LaCrO 3 were the chosen materials. Samples were characterized by means of X-ray diffraction, scanning electron microscopy, BET surface area, temperature programmed reduction and X-ray photoelectron spectroscopy. Reactions tested have been soot oxidation by 10% O 2 and 0.5% NO and stoichiometric 1% NO reduction by 1% CO. LaMnO 3 has proved to be a good catalyst for oxidation reactions, whereas LaCrO 3 is more suitable for reduction reactions. TPR and XPS analysis have shown a greater oxygen exchange capability in LaMnO 3 than in LaCrO 3 , which is less reducible and strongly bonds adsorbed oxygen. Substitution of 20% La in the A-site of the perovskitic lattice with K has increased activity of both catalysts. In the case of LaCrO 3, however, this has lead to a slower reaction course. NO reduction test clearly indicates that Cr-containing perovskite is more suitable for reduction reactions, whereas Mn-based materials are a good choice for oxidative applications. This can relate to superficial oxygen properties and bulk oxygen mobility, as shown by XPS and TPR results.